The bio-signal could be used to evaluate and diagnose the important parameters for biological status, which employs the analysis on the bio-signal to be provided as the reference of clinical diagnosis. The bio-signal is characterized in having a periodically changing signal. The commonly used bio-signal includes the electrocardiogram (ECG or EKG, although both signals are well known in this field as the same signal, but for purpose of present invention, the electrocardiogram will be referred as ECG), Heart Sound or Respiration Signal, which could be used to evaluate the cardiovascular system and lung function respiration system. The basic principles are briefly described as follows.
As shown in FIG. 1, the heart structure could be divided as two portions, the atrium and the ventricle, in which the atrium portion is connected with the upper and lower chamber veins. When the right atrium is full of the blood returned by the veins, the sinoatrial node (101) on the right atrium will spontaneously generate the depolarized action potential. The current signal will be transmitted to the left atrium through the muscle cells of the atrium. Because the muscle cells of the heart is provided with the ion channels suitable for electrical connection, the signal transmission is very fast, so that the left and right atriums will almost simultaneously depolarized, and further generate the contraction of muscle fibers, and generate the mechanical energy power to extrude the blood into the ventricle. At this time, the depolarized current signal will be transmitted to the atrio-ventricular node (102) at the bottom of the right ventricle. Because the signal transmission speed of the atrio-ventricular node is slower, the ventricle will have enough time to complete the operation of depolarized contraction.
Next, the atrio-ventricular node will transmit the depolarized current signal to the entire left and right atriums through the Purkinje fibers (106), so the left and right ventricles are depolarized contraction simultaneously, and extrude the blood to the upper and lower chamber arteries, and accomplish a complete heart beat cycle. It could be noted that the heart employs the weak nerve current signal transmission to achieve the contraction and diastole action. Because the human body is a conductor, the current will conduct and flow all over the body through the human tissues. At this time, if attaching the conductible electrode patch on the body surface, it could employ the signal abscontraction circuit to record the current signal, and this signal is referred as the electrocardiogram (ECG or EKG) signal.
Generally in the ECG of so-called second leads body surface electrode record, the main signal composition is shown in FIG. 2A, which includes a P-wave representing the waveform signal measured and recorded on the body surface when the atrium is depolarized contraction, in which the measured and recorded is a QRS composite wave after about 0.15 seconds representing the depolarized contraction of the ventricle. At the same time, the ventricle will have the repolarized diastolic effect. But the repolarized signal strength of the ventricle is smaller than the depolarized signal strength, it could not be observed in ECG. The final T-wave represents the signal measured and recorded during repolarized diastole of the atrium. It could be found in the associated research, in various clinic diagnosis of diseases, the ECG will be appeared to present abnormal waveform or abnormal variation, such as ventricular hypertrophy, arrhythmia, myocardial infarction, coronary artery incompetence, and the like.
The heart sound signal is recorded with the sound given when the heart valve is closed. The most easily observed is the first heart sound (S1) and the second heart sound (S2), as shown in FIG. 2B. In the clinic, if the heart has the abnormal condition in the biological structure, besides of S1 and S2, there will be other murmur occurring. As shown in FIG. 2C, the signal occurred between S1 and S2 is the murmur, which is an important basis for determining heart disease.
Biologically, the speed of heart beat is controlled by various mechanisms, in which one of the important mechanisms is the respiration, and the speed of respiration will cause the variation of blood oxygen density, which will indirectly affect the heart rate. FIG. 2D shows the measurement result of the respiration signal.
In the method for analyzing bio-signal, the major domains have two portions: one is the analysis of frequency domain, which employs the fast Fourier Transform (FFT) to calculate the power spectrum of the bio-signal and observe the variance in the frequency domain. For example, in the analysis of heart rate variability (HRV) for calculating the ratio of band energy of LF (0.04˜0.15 Hz) and HF (0.15˜0.4 Hz), it is to observe the effect of the sympathetic nerve and the parasympathetic nerve to the heart rate variation; another one is to observe the waveform variance of the bio-signal, which is based on the analysis of Chaos Theory to understand the waveform distortion effect on the bio-signal caused by the disease, in which the commonly used analysis is the phase space matrix reconstruction. In the CPSD (Chaotic Phase Space Difference) algorithm, it employs the calculation of CPSD to generate the reference data for determining the bio-signal. For the application of ECG, it first could be used to calculate the heart rate, which has replaced the conventional R-R interval calculation method, and effectively solved the problem of threshold value selection in R-R interval calculation, and it could further easily determine the normal and abnormal ECG signal. In the application of heart sound, it could employ the CPSD algorithm to distinguish S1 and S2 to differentiate the murmur, and calculate the heart rate instantaneously. In the application of respiration signal, the CPSD algorithm could be used to calculate the variance of respiration rate.
In WO 2004/023995 published on Mar. 25th, 2004, it disclosed a device and method for measuring subcutaneous ECG waveform through the R-wave algorithm. The device is mainly used for implanted defibrillator or inserted loop recorder, and employs the interval difference between R-wave and R-wave to determine if arrhythmia has occurred and as the basis of recording and defibrillating. In the calculation of measurement method, employing the R-wave algorithm and the automatic threshold value regulation method to precisely abstract the R-wave message as the basis of calculation of interval difference between R-waves.
Although using the interval difference between R-waves as the measurement method for ECG has been disclosed in the content of the prior art, using the interval difference between R-waves as the ECG measurement method will be limited by the selection of the threshold, which could not easily and rapidly differentiate the difference between normal and abnormal ECG signals. In order to solve this problem, it is required an ECG analysis method for easily editing, fast processing speed, saving the storage space, and reducing consumed system resources.
U.S. Pat. No. 5,794,623 teaches using electrocardiogram (ECG) signals from a body to analyze the irregular intramyocardial Wenckebach activity (MWA) in the heart of a patient. This prior art discloses using a mechanism for measuring respiratory signals from the body and a processor electrically associated with the two mechanisms means for measuring the presence of intramyocardial Wenckebach activity of two or more phases. The Wenchebach basis function strengths is calculated by the processor to indicate the presence of voltage in the measured ECG signals caused by the repeating patterns of irregular intramyocardial Wenckebach activity via a relationship that describes the measured ECG signals as comprising Wenckebach input being additive to respiratory interference. This conventional method is suitable for calculate the interference and noise by analyzing the breathing signal of the patient and myocardial Wenckebach activity to classify ventricular fibrillation but is not appropriate for analyzing the periodical bio-signal by CPSD.
U.S. Pat. No. 5,643,325 discloses a method for detecting a hear disorder by using a phase-plan plot (PPP) of a patient electrocardiogram (ECG). The PPP's degree of deterministic chaos is measured by a processor, and the PPP result is analyzed by Lyapunov exponent or Poincare section method to indicate the risk of fibrillation and its actual onset where the risk is 100 percent. The prior art further teaches using a frequency-domain transform (such as an FFT) of a patient ECG. Nth derivative theorem is employed to use a plot of variable of ECG signals, such as voltage, and derivative value (dV/dt, d2 V/dt2) to construct a phase-plane plot (ppp) from ECG signal in which the funnel area of the PPP exhibits an irregular and highly complex pattern, indicative of ventricular fibrillation. The main objective of U.S. Pat. No. 5,643,325 is to determine that when a normal patient have a PPP which exhibits the regularity and smoothness of an ECG signal from that normal patient, while a patient undergoing VF will have a PPP which exhibits the irregularity and complexity of an ECG signal which might be deterministic chaos (e.g., a periodicity, banding and “forbidden zones”). When a patient in transition from normal into VF (i.e., in VF onset) exhibits a PPP which is consistent with an assessment that the ECG signal for the patient is in transition to deterministic chaos. One of major drawback of this conventional technique is that the analyzing and processing are labor intensive in which the data have to be analyzed and calculated through a complex method, and it is suit for ventricular fibrillation analysis only. In other words, this conventional technique is difficult and time-consuming to process and assess all the data.